(a) Technical Field
The present disclosure relates to a water reservoir for a vehicle. More particularly, it relates to a cooling water reservoir for a fuel cell vehicle, which stores and supplies cooling water for cooling a fuel cell stack during operation and, at the same time, collects product water generated in the fuel cell stack.
(b) Background Art
A fuel cell system generates electrical energy by electrochemically converting chemical energy derived from a fuel directly into electrical energy by oxidation of the fuel.
The fuel cell system comprises a fuel cell stack for generating electricity by electrochemical reaction, a hydrogen supply system for supplying hydrogen as a fuel to the fuel cell stack, an oxygen (air) supply system for supplying oxygen containing air as an oxidant required for the electrochemical reaction in the fuel cell stack, a thermal management system (TMS) for removing reaction heat from the fuel cell stack to the outside of the fuel cell system, controlling operation temperature of the fuel cell stack, and performing water management function, and a system controller for controlling overall operation of the fuel cell system.
The fuel cell system having the above configuration generates electricity by the electrochemical reaction using hydrogen as the fuel and oxygen containing air and discharges heat and water as by-products.
Since the fuel cell system generates heat as a by-product, the system should be equipped with an apparatus for cooling the fuel cell stack to prevent an increase in the temperature of the fuel cell stack.
FIG. 1 is a schematic diagram of a cooling system for a fuel cell vehicle, in which a two-loop system is shown.
As shown in FIG. 1, the cooling system comprises a first cooling loop 10 and a second cooling loop 14. An intermediate heat exchanger 12 is used to cool a fuel cell stack 11. In the first cooling loop 10, cooling water is circulated through the fuel cell stack 11, the intermediate heat exchanger 12, and a circulation pump 13. In the second cooling loop 14, cooling water is circulated through a circulation pump 15, the intermediate heat exchanger 12, and a radiator 16.
In more detail, the cooling water circulated through the first cooling loop 10 by the circulation pump 13 passes through a cooling water line of the fuel cell stack 11 to remove heat from the fuel cell stack 11, and then the cooling water of the first cooling loop 10 transfers heat to the cooling water circulating through the second cooling loop 14 at the intermediate heat exchanger 12.
The cooling water of the second cooling loop 14, which receives heat from the cooling water of the first cooling loop 10 at the intermediate heat exchanger 12, radiates heat while passing through the radiator 16 and is then cooled. As a result, reaction heat of the fuel cell stack 11 is removed by the cooling water of the first cooling loop 10, the intermediate heat exchanger 12, the cooling water of the second cooling loop 14, and the radiator 16.
In this case, when the cooling system is turned off, the cooling water in the first cooling loop 10 for primarily cooling the fuel cell stack 11 flows from the first cooling loop 109 to the bottom of the cooling system by gravity and is collected in a cooling water reservoir (water tank) 20 mounted at the bottom of the vehicle. When the cooling system is turned on and a vacuum state is created inside the system by a suction pump, the water in the reservoir 20 flows up to the inside of the system by a pressure difference.
The cooling water reservoir having the above functions must satisfy the sealing requirements of connection portions and have the capability of efficiently supplying the cooling water to the cooling system in a vacuum state.
FIG. 2 is a perspective view showing a conventional reservoir for a fuel cell vehicle. A reservoir 20 having a predetermined space in which cooling water (including product water) is stored comprises a reservoir housing 21 having a predetermined inner space, a cover 22 covering the top of the reservoir housing 21, and a plurality of ports 23 to 26 installed at the top of the cover 22.
The plurality of ports 23 to 26 include an intake port 23 connected to the suction pump 17 of FIG. 1 such that the cooling water is drawn from the inner space of the reservoir housing 21 through the intake port 23 and supplied to the cooling water line during operation of the suction pump 17. The cooling water flowing through the intake port 23 is supplied to the cooling water line of the first cooling loop in the cooling system of FIG. 1 and then circulated.
Since the intake port 23 extends to the bottom of the reservoir housing 21, it can suck the water at the bottom of the reservoir housing 21, and therefore it is possible to stably supply water even if the vehicle is inclined on a slope.
Moreover, the plurality of ports 23 to 26 include a cooling water collection port 24 through which the cooling water in the cooling water line is collected when the vehicle is turned off, a product water inlet port 25 connected to the fuel cell stack 11 to extract product water from the fuel cell stack 11, and an overflow port 26 through which excess water in the inner space of the reservoir housing 21 is discharged.
The above-described reservoir for a fuel cell vehicle is mounted at the bottom of the vehicle such that the water in the cooling water line is collected therein by gravity when the fuel cell system is turned off and the cooling water in the reservoir is supplied to the cooling water line of the cooling system by the operation of the suction pump when the fuel cell system is turned on.
Korean Patent Application No. 2007-0130091, for example, discloses a cooling water reservoir for a fuel cell vehicle. However, the conventional reservoir has a problem that a considerable amount of product water overflows when the fuel cell system is turned off. That is, the product water generated during traveling of the vehicle is collected in real-time in the reservoir (water tank) and, further, the cooling water in the cooling water line flows down to the reservoir when the vehicle is turned off. As a result, a considerable amount of water overflows on the surface of the parking lot where the vehicle after being driven is parked.
In more detail, the product water generated in the fuel cell stack is collected in the reservoir mounted at the bottom of the vehicle during traveling of the vehicle. Moreover, when the vehicle is turned off, the cooling water circulating through the cooling water line is also collected in the reservoir. Accordingly, the water remaining in the reservoir, the product water generated in the fuel cell stack during traveling of the vehicle, and the water in the cooling water line are all collected in the reservoir. As a result, the water in an amount exceeding the reservoir capacity overflows on the surface of the parking lot.
For example, if about 13 L water is pumped from the reservoir containing about 16 L water to the cooling water line during start-up of the fuel cell vehicle, about 3 L water remains in the reservoir. Then, if product water (α L) generated in the fuel cell stack during traveling of the vehicle flows down and is collected in real-time in the reservoir, the amount of collected water is (3+α) L. Subsequently, when the vehicle is turned off, 12 L cooling water in the cooling water line flows down to the reservoir. As a result, the amount of water in the reservoir is (16+α) L, and a L water exceeding the reservoir capacity is discharged through the overflow port to the surface of the parking lot.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.